Currently, there are numerous Institute of Electrical and Electronics Engineers (IEEE) standards for Ethernet. Some examples are 10BaseT, 100BaseT, and 1000BaseT, which are enumerated and described for several different types of transmission media (i.e., twisted-pair). Specifically, though, 100BaseT for twisted-pairs (which is described by IEEE 802.3u and that is hereby incorporated by reference for all purposes) has largely fallen into disuse in favor of higher speed standards (i.e., 1000BaseT) with exception to many industrial applications. In other words, 100BaseT is still widely used for industrial Ethernet.
Generally, 100BaseT allows for the establishment of links on cables (such as Category 5 or CAT5 cables) up to 120 m or more in length. In a given industrial Ethernet system, many of the cables deployed will be less than 120 m in length, and, in fact, many of the cables are much shorter than 120 m. Yet, the transmission amplitude output from each unit is generally the same, regardless of cable length. Usually, in these shorter cables the 100BaseT physical layer (PHY) attenuates incoming signals, resulting in wasted power on transmission. Because of the limited and relatively small market for 100BaseT, there has been very little development, even though there are problems that exist (such as wasted power on transmission). Thus, there is a need for a system that more efficiently uses power over 100BaseT connections.
An example of conventional systems is PCT Publ. No. WO08/027,671.